Re: Extending my question. Was: The relational model and relational algebra - why did SQL become the industry standard?

jan.hidders_at_REMOVE.THIS.ua.ac.be (Jan Hidders) wrote in message > Well, your specific example involves recognizing that duplicate elimination
> is not necessary in the view. That was something that was researched as
> (relatively) recently as 1994:
>
> http://www.informatik.uni-trier.de/~ley/db/conf/icde/PaulleyL94.html

The subject has been covered even earlier in a paper by Hugh Darwen published in Relational Database Writings 1989-1991. The name of the paper is "The Role of Functional Dependence in Query Decomposition". It provides an algorithm for deriving all candidate keys from a relational expression (or view).

regards,
Lauri Pietarinen Received on Mon Mar 10 2003 - 13:24:40 CST